the epa's regulatory power over the coal industry, power the president has backed while pushing green energy sources. and a growing number of democrats like louisiana's mary landrieu, facing a tough re-election fight this fall, are publicly pressuring the president to approve the keystone pipeline. there's also concern about how solid democrat support would be for a strong push on controversial issues the administration has struggled to advance, like beefing up gun control. as his approval ratings are hitting a new low, the president's powers of persuasion may also be receding, and the star power he once brought to the campaign trail appears to be cooling for democrats locked in heated races. >> he's not even showing up in their home states. sending bill clinton and michelle obama, everyone but the president, so, listen, his popularity is down. this whole obamacare thing is a mess, fast and furious, benghazi, i can go on and on >> reporter: latest showdown between the white house and senate democrats is over a new round of sanctions for iran. there is a measure which has bipartisan support u